CN110180994B - Preparation method of investment casting shell with long and thin blind holes - Google Patents
Preparation method of investment casting shell with long and thin blind holes Download PDFInfo
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- CN110180994B CN110180994B CN201910551439.6A CN201910551439A CN110180994B CN 110180994 B CN110180994 B CN 110180994B CN 201910551439 A CN201910551439 A CN 201910551439A CN 110180994 B CN110180994 B CN 110180994B
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- shell
- blind hole
- wax
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- rod
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
- B22C7/02—Lost patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/04—Use of lost patterns
Abstract
The invention discloses a preparation method of an investment casting shell with a long and thin blind hole, which comprises the following steps of; 1. manufacturing a wax mould slim rod and a wax mould of the body casting, wherein the diameter of the wax mould slim rod is smaller than that of the blind hole of the body casting, and the length of the wax mould slim rod is larger than that of the blind hole of the body casting; 2. coating a shell on the wax mould thin rod; 3. inserting the wax mould thin rod coated with the shell into the blind hole of the wax mould of the body, and injecting refractory slurry into the gap between the blind hole and the wax mould thin rod; 4. after the refractory slurry is naturally dried, coating and hanging an integral shell; 5. after the integral shell is coated and hung, grinding the wax pattern slender rod part extending out of the blind hole part to expose the inner wax pattern, and dewaxing the integral wax pattern and the wax pattern slender rod; 6. and roasting the integral shell after wax removal to obtain the shell of the investment casting. The method solves the problem of preparing the shell of the investment casting with the elongated blind hole, ensures the strength of the shell in the blind hole, avoids the phenomenon of fire leakage of the casting during pouring, and eliminates the defect of defect in the blind hole.
Description
Technical Field
The invention belongs to the field of precision investment casting, and relates to a preparation method of an investment casting shell with a long and thin blind hole.
Background
The investment casting is also called lost wax casting, which is that soluble material is made into investment and combined with a module, then the surface of the module is coated with a plurality of layers of refractory materials, after drying and solidification, a shell is formed, the shell is heated to melt out the mould material, and then the molten metal is poured into the shell after high-temperature roasting, thus obtaining the investment casting.
In investment casting, shell preparation is one of the important processes, and the quality of the shell directly influences the quality of a casting. The shell is generally prepared by coating. The refractory slurry is coated on the wax mould set, then the excessive paste is removed, the refractory sand grains are sprinkled on the wax mould set, and then the coating is dried and hardened to form a first layer of shell outside the mould set. Repeating the operation for many times to form a multi-layer firm shell outside the module. According to the difference of part shape and size, 4 ~ 5 layers of shell need be made to the smallclothes usually, and 7 ~ 8 layers of shell just can obtain required shell intensity need be made to the major possession, that is to say need 4 layers of shell at least can guarantee that the shell has sufficient intensity usually, avoid being unlikely to take place "the phenomenon of running out" after the molten metal gets into the shell, cause the foundry goods to form incomplete sex defect, lead to the foundry goods to scrap even.
For the casting with the slender blind hole, because the slender blind cavity is arranged, refractory slurry is difficult to coat and the floating sand in the hole is difficult to clean, so that when about 2 layers of coating and hanging are coated and hung, the hole is blocked and can not be coated and hung repeatedly, the strength of a local shell in the hole is insufficient, the phenomenon of 'fire running' occurs during pouring, the casting forms incomplete defects, and even the casting is scrapped.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a preparation method of an investment casting shell with a long and thin blind hole, so that the strength of the investment casting shell with the long and thin blind hole is improved, the polishing and repairing amount of a cast after pouring is reduced, and the waste loss of parts is reduced.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
a method for preparing an investment casting shell with a long and thin blind hole comprises the following steps;
firstly, manufacturing a wax mould slim rod and a wax mould of a body casting, wherein the diameter of the wax mould slim rod is smaller than that of a blind hole of the body casting, and the length of the wax mould slim rod is larger than that of the blind hole of the body casting;
coating and hanging 3-5 layers of shells on the wax mould thin rod by adopting the same coating and hanging process as the body casting;
inserting the wax mould thin rod coated with the shell into the blind hole of the wax mould body, and injecting refractory slurry into the gap between the blind hole and the wax mould thin rod;
step four, after the refractory slurry is naturally dried, coating and hanging an integral shell;
step five, after the coating of the integral shell is finished, grinding the part of the wax pattern slim rod extending out of the blind hole part to expose the inner wax pattern, and dewaxing the integral wax pattern and the wax pattern slim rod;
and step six, roasting the integral shell after wax removal to obtain the shell of the investment casting.
Preferably, in the first step, the diameter of the wax mould slim rod is 3 mm-5 mm smaller than the diameter of the body casting blind hole, and the length of the wax mould slim rod is 8 mm-10 mm larger than the length of the body casting blind hole.
Furthermore, the diameter of the wax mould slim rod is 5mm smaller than the diameter of the body casting blind hole, and the length of the wax mould slim rod is 10mm larger than the length of the body casting blind hole.
Preferably, in the second step, the wax pattern slim rod is coated with 4 layers of shell molds.
Further, in the second step, the first layer of the coating shell of the wax mould slim rod is coated with silica sol-zircon powder with the viscosity of 40-50 s, then is sanded with 70# corundum sand, and is coated with the second layer after the self-drying time is more than or equal to 12 hours; coating and hanging the second layer by adopting ethyl silicate hydrolysate-shop powder with the viscosity of 37-42 s, then sanding by adopting 36# shop sand, and coating and hanging the third layer to the fourth layer after the self-drying time is more than or equal to 20 minutes and the ammonia drying time is 10 minutes; and coating each of the third to fourth layers by adopting ethyl silicate hydrolysate-shop powder with the viscosity of 13-15 s, and then sanding by adopting No. 24 shop sand, wherein the coating of the wax pattern thin rod is completed after the self-drying time is more than or equal to 20 minutes and the ammonia drying time is 10 minutes.
Preferably, in the third step, the silica sol-zircon powder is adopted as the refractory slurry.
Preferably, in step four, the refractory slurry is naturally dried for a period of at least 12 hours.
Preferably, in the fourth step, the number of coating layers of the integral shell is 8-10.
Further, the number of coating layers of the integral shell is 10, the first coating layer of the integral shell is firstly coated with silica sol-zircon powder with the viscosity of 40-50 s, then sanding is carried out by using No. 70 corundum sand, and after the self-drying time is more than or equal to 12 hours, the second coating layer is carried out; the second layer is firstly coated with ethyl silicate hydrolysate with the viscosity of 37-42 s, namely powder in the shop, and then is coated with 36# shop sand, and after the self-drying time is more than or equal to 20 minutes and the ammonia drying time is 10 minutes, the third to ninth layers are coated; coating each of the third to ninth layers by adopting ethyl silicate hydrolysate-shop powder with the viscosity of 13-15 s, then sanding by adopting No. 24 shop sand, and coating a sealing layer after the self-drying time is more than or equal to 20 minutes and the ammonia drying time is 10 minutes; the sealing layer is coated by adopting ethyl silicate hydrolysate with slurry viscosity of 13-15 s-shop powder, and the whole coating is completed after the self-drying time is more than or equal to 12 hours.
Preferably, in the fifth step, the shell after wax removal is placed into a roasting furnace for roasting, the roasting temperature is 840-860 ℃, and the shell is taken out after heat preservation for 1-1.5 hours.
Compared with the prior art, the invention has the following beneficial effects:
the method comprises the steps of preparing a wax pattern slim rod in advance before preparing a shell by using an integral wax pattern, coating the shell on the wax pattern slim rod, putting the prepared slim rod shell into a slender blind hole of the wax pattern, injecting refractory slurry into a gap between the slender blind hole and the slim rod shell, and coating the shell after the refractory slurry is dried.
Drawings
FIG. 1 is a schematic view of a wax pattern of a body casting of the present invention;
FIG. 2 is a schematic view of a wax pattern slim rod of the present invention;
FIG. 3 is a schematic view of a wax pattern slim rod coated shell of the present invention;
FIG. 4 is a schematic view of a wax pattern slim rod inserted into a body wax pattern of the present invention;
FIG. 5 is a schematic view of the injected refractory slurry of the present invention;
FIG. 6 is a schematic view of the one-piece shell coating of the present invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
as shown in FIG. 1, the method for preparing the investment casting shell with the elongated blind hole comprises the following steps:
firstly, manufacturing a wax mould slim rod and a wax mould of a body casting, wherein the diameter of the wax mould slim rod is 3-5 mm smaller than the diameter of a blind hole of the body casting, and the length of the wax mould slim rod is 8-10 mm larger than the length of the blind hole of the body casting.
And step two, coating and hanging 3-5 layers of shells on the wax mould thin rod by adopting the same coating and hanging process as the body casting.
And step three, inserting the wax pattern slim rod coated with the shell into the blind hole of the wax pattern body, and injecting refractory slurry into the gap between the blind hole and the wax pattern slim rod.
And step four, after the refractory slurry is naturally dried, coating and hanging the integral shell, wherein the number of the coating and hanging layers of the integral shell is 8-10.
And step five, after the integral shell is coated, grinding the wax pattern thin rod part extending out of the blind hole part to expose the inner wax pattern, and dewaxing the integral wax pattern and the wax pattern thin rod.
And sixthly, putting the shell subjected to wax removal into a roasting furnace for roasting at the roasting temperature of 840-860 ℃, preserving heat for 1-1.5 hours, and discharging to obtain the shell of the investment casting.
The specific implementation process is as follows; the casting material is austenitic stainless steel ZG1Cr18Ni9Ti, and the casting contains a blind hole with the diameter of phi 15mm and the length of 20 mm. As the casting blind hole is provided with the slender blind hole, refractory slurry is difficult to coat and the floating sand in the hole is difficult to clean, so that when about 2 layers of coating and hanging are coated and hung, the hole is blocked and can not be coated and hung repeatedly, the strength of a local shell in the hole is insufficient, the phenomenon of 'fire running' occurs during pouring, a casting forms a defect of incomplete property, and the repair rate of the casting blind hole reaches 95 percent.
The preparation process comprises the following steps: the first step is as follows: pressing a wax pattern thin rod with the diameter of phi 10mm and the length of 30 mm.
The second step is that: and coating and hanging the 4-layer shell on the wax mould thin rod which is formed by pressing according to the shell coating and hanging process of the body casting. The coating parameters are shown in Table 1.
TABLE 1
The third step: the wax mould thin rod coated with the 4-layer shell is inserted into the slender blind hole of the wax mould body, and a proper amount of surface layer refractory slurry (namely the first layer of silica sol-zircon powder) is injected into a gap between the slender blind hole and the thin rod shell.
The fourth step: and after the refractory slurry is naturally dried for 12 hours, normal shell coating can be carried out. The coating parameters are shown in Table 2.
TABLE 2
The fifth step: after the shell is coated, the end part of the wax mould slim-rod shell with the exposed slender blind hole part is ground by using a grinding wheel to expose a wax mould, and then the whole wax mould is placed into a high-pressure dewaxing kettle for dewaxing.
And a sixth step: and (3) putting the shell subjected to wax removal into a roasting furnace, keeping the roasting temperature at 850 +/-10 ℃ for 1 hour, and discharging to obtain the shell of the investment casting.
After the shell manufacturing process of the prefabricated blind hole shell is adopted, the problem of shell manufacturing of the investment casting with the elongated blind hole of the casting is solved, the strength of the shell in the blind hole is guaranteed, the casting does not generate a fire running phenomenon during pouring, the defect of defect in the blind hole is eliminated, and the quality qualification rate of the inner surface of the blind hole of the casting is 100%.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (7)
1. The preparation method of the investment casting shell with the elongated blind hole is characterized by comprising the following steps of;
firstly, manufacturing a wax mould slim rod and a wax mould of a body casting, wherein the diameter of the wax mould slim rod is smaller than that of a blind hole of the body casting, and the length of the wax mould slim rod is larger than that of the blind hole of the body casting; the diameter of the wax mould slim rod is 3 mm-5 mm smaller than the diameter of the body casting blind hole, and the length of the wax mould slim rod is 8 mm-10 mm larger than the length of the body casting blind hole;
coating and hanging 3-5 layers of shells on the wax mould thin rod by adopting the same coating and hanging process as the body casting;
inserting the wax mould thin rod coated with the shell into the blind hole of the wax mould body, and injecting refractory slurry into the gap between the blind hole and the wax mould thin rod;
step four, after the refractory slurry is naturally dried, coating and hanging an integral shell, wherein the natural drying time of the refractory slurry is at least 12 hours;
step five, after the coating of the integral shell is finished, grinding the part of the wax pattern slim rod extending out of the blind hole part to expose the inner wax pattern, and dewaxing the integral wax pattern and the wax pattern slim rod;
and step six, roasting the integral shell after wax removal to obtain the shell of the investment casting.
2. The method for preparing an investment casting shell with elongated blind holes according to claim 1, wherein in the second step, the wax pattern slim rod is coated with 4 layers of shells.
3. The method for preparing the investment casting shell with the elongated blind hole according to claim 2, wherein in the second step, the first layer of the coating shell of the wax pattern slim rod is coated with silica sol-zircon powder with the viscosity of 40-50 s, then is sanded with No. 70 corundum, and is coated with the second layer after the self-drying time is more than or equal to 12 hours; coating and hanging the second layer by adopting ethyl silicate hydrolysate-shop powder with the viscosity of 37-42 s, then sanding by adopting 36# shop sand, and coating and hanging the third layer to the fourth layer after the self-drying time is more than or equal to 20 minutes and the ammonia drying time is 10 minutes; and coating each of the third to fourth layers by adopting ethyl silicate hydrolysate-shop powder with the viscosity of 13-15 s, and then sanding by adopting No. 24 shop sand, wherein the coating of the wax pattern thin rod is completed after the self-drying time is more than or equal to 20 minutes and the ammonia drying time is 10 minutes.
4. The method for preparing an investment casting shell with elongated blind holes according to claim 1, wherein silica sol-zircon powder is used as the refractory slurry in the third step.
5. The method for preparing the investment casting shell with the elongated blind hole according to claim 1, wherein in the fourth step, the number of coating layers of the integral shell is 8-10.
6. The method for preparing the investment casting shell with the elongated blind hole according to claim 5, wherein the number of the integral shell coating layers is 10, the first integral shell coating layer is firstly coated with silica sol-zircon powder with the viscosity of 40-50 s, then is sanded with No. 70 corundum, and the second integral shell coating layer is carried out after the self-drying time is more than or equal to 12 hours; the second layer is firstly coated with ethyl silicate hydrolysate with the viscosity of 37-42 s, namely powder in the shop, and then is coated with 36# shop sand, and after the self-drying time is more than or equal to 20 minutes and the ammonia drying time is 10 minutes, the third to ninth layers are coated; coating each of the third to ninth layers by adopting ethyl silicate hydrolysate-shop powder with the viscosity of 13-15 s, then sanding by adopting No. 24 shop sand, and coating a sealing layer after the self-drying time is more than or equal to 20 minutes and the ammonia drying time is 10 minutes; the sealing layer is coated by adopting ethyl silicate hydrolysate with slurry viscosity of 13-15 s-shop powder, and the whole coating is completed after the self-drying time is more than or equal to 12 hours.
7. The preparation method of the investment casting shell with the elongated blind hole according to claim 1, wherein in the fifth step, the shell after wax removal is placed into a roasting furnace for roasting, the roasting temperature is 840-860 ℃, and the shell is discharged after heat preservation is carried out for 1-1.5 hours.
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| CN110640085A (en) * | 2019-10-29 | 2020-01-03 | 贵州安吉航空精密铸造有限责任公司 | Investment casting process for hollow casting |
| CN111001759A (en) * | 2019-11-11 | 2020-04-14 | 湖州南丰机械制造有限公司 | Shell making method for improving sand removing efficiency of casting |
| CN111992679A (en) * | 2020-08-24 | 2020-11-27 | 贵州安吉航空精密铸造有限责任公司 | Coating method for thin-wall hollow casting shell |
| CN112620580B (en) * | 2020-12-23 | 2023-05-26 | 安徽应流铸业有限公司 | Shell making process for long hole castings |
| CN113695517A (en) * | 2021-08-25 | 2021-11-26 | 贵州安吉航空精密铸造有限责任公司 | Preparation method of shell of titanium alloy investment casting with long and narrow through hole |
| CN114406190A (en) * | 2021-12-28 | 2022-04-29 | 东营一诚精密金属有限公司 | Process method for ensuring coaxiality of investment casting blind holes |
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| JPH0716700A (en) * | 1993-06-30 | 1995-01-20 | Daido Steel Co Ltd | Wax pattern used to manufacture of mold and method for coating refractory sand |
| CN102773412B (en) * | 2012-08-16 | 2014-10-29 | 安徽应流集团霍山铸造有限公司 | Shell making method for deep blind hole of precision casting |
| CN104493091A (en) * | 2014-12-15 | 2015-04-08 | 贵州安吉航空精密铸造有限责任公司 | Investment casting method of aluminum alloy pores |
| CN107520406B (en) * | 2017-09-12 | 2021-08-24 | 东方电气集团东方汽轮机有限公司 | Precision casting method for long cylindrical part |
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